Rechargeable electrochemical elements, in particular lithium cells, in many cases contain a cell stack which comprises two or more individual elements. The individual cells or individual elements from which a cell stack such as this is composed are a laminate which is produced from output conductors, an active electrode film and a separator. Laminates such as these composed of firmly connected individual parts are produced in particular as so-called—“bicells”— with the following possible sequences: negative electrode/separator/positive electrode/separator/negative electrode, or positive electrode/separator/negative electrode/separator/positive electrode.
Methods for producing such rechargeable lithium ion batteries are described in U.S. Pat. No. 5,460,904. Two or more bicells are arranged in layers to form a stack which, after insertion into a container composed, for example, of thermoformed aluminum composite sheet, filling with electrolyte, sealing with a cover, formation and final closure, is processed to form a complete battery.
Highly automated measurement devices are used for electrical testing of batteries in the battery industry. In the field of rechargeable batteries, these systems are also able to form the batteries by carrying out one or more charge/discharge cycles. In order to achieve high throughput rates, these systems are in general fully automated.
The formation of a large number of electrochemical elements requires complex apparatuses, in which electrical contact is made with the output conductors of the cells during the formation process, and in which the cells are held. In general, a large number of flat cells are inserted alongside one another into recesses in a holder, a so-called—“formation tray,”— with the recesses being matched to the cell cross section. In this case, the output conductor lugs of the flat cells point in one direction and are, for example, clamped in between contact springs which are in the form of plates and are arranged on mount apparatuses. However, contact can also be made with the output conductor lugs by pushing contact pins onto them.
During the testing of the battery characteristics, the batteries are measured serially, that is to say one after another, with the test duration generally being less than 1 second. Longer lasting tests or operations are, however, carried out with two or more batteries in parallel, that is to say at the same time. For this purpose, the batteries are introduced into special containers and are supplied to the appropriate system automatically or by hand. These systems are generally computer-controlled, and defective batteries are segregated automatically. The test or operation is carried out with constant currents or current pulses and/or constant voltages. An apparatus such as this is known, for example, from DE 102 13 685.8 A1.
The contact-making devices are provided with connecting cables corresponding to the number of batteries, and have four connections per cell. Several thousand or ten thousand batteries are usually processed at the same time in systems for battery formation. Each individual battery is connected to one channel of the control, measurement and regulation electronics. The large number of cables and control electronics channels that this results in can lead to faults both during installation and during operation.
Manual testing of the connections during construction of the system is highly complex, requiring a long time and a large amount of work in difficult conditions. Faults can often not be detected during operation, and this thus leads to incorrect measurements and incorrect actions.